Magnetic, thermodynamic and transport properties of GdFe$_{2}$(Al$_{x}$Zn$_{1-x})_{20}$

The unusual physical properties of the dilute, rare-earth-bearing, intermetallic compound GdFe$_{2}$Zn$_{20}$ have been explained as being the result of the Gd$^{3+}$ moment being embedded in a nearly ferromagnetic Fermi liquid. To understand this in detail, single crystals of the pseudo ternary series GdFe$_{2}$(Al$_{x}$Zn$_{1-x})_{20}$(x $\le $0.07) and YFe$_{2}$(Al$_{x}$Zn$_{1-x})_{20}^{ }$(x $\le $0.05) were grown out of Zn-rich solution. Magnetization, heat capacity and resistivity measurements on these compounds reveal a decrease of T$_{c}$ from 86 K (x = 0) to 4 K (x = 0.07) for GdFe$_{2}$(Al$_{x}$Zn$_{1-x})_{20}$ and a decrease of the Stoner enhancement factor, Z, from 0.88 (x = 0) to 0.35 (x = 0.05) for YFe$_{2}$(Al$_{x}$Zn$_{1-x})_{20}$. Rigid band approximation and TB-LMTO-ASA calculation are used to explain this trend. These results, combined with earlier studies of the substitution of Co for Fe clearly indicate the importance of band filling and the applicability of even a simple rigid band model, to these compounds.